Author Topic: HP8751A network analyzer schematic needed  (Read 4138 times)

0 Members and 1 Guest are viewing this topic.

Offline mrf245Topic starter

  • Regular Contributor
  • *
  • Posts: 79
  • Country: cn
HP8751A network analyzer schematic needed
« on: March 21, 2015, 05:01:56 am »
Hi,I have HP8751A with some issue with power module and need to fix it,and I found operation and calibration manual from HP website,but no schematic and description for that.I don't know if anyone have it and may share to me,I'll really appreciate you,thanks.
« Last Edit: March 21, 2015, 05:09:41 am by mrf245 »
BH7JUO Mark
 

Offline acbern

  • Frequent Contributor
  • **
  • Posts: 316
  • Country: de
Re: HP8751A network analyzer schematic needed
« Reply #1 on: March 21, 2015, 08:03:29 am »
I think the PSU is the same as in the 8720A/B/C VNAs. These are available. Download and check against the different versions.
If that turns out to be correct, keep us posted please about the version (not even sure there are much/any differences, its been a while since I repaired mine).
 

Offline mrf245Topic starter

  • Regular Contributor
  • *
  • Posts: 79
  • Country: cn
Re: HP8751A network analyzer schematic needed
« Reply #2 on: March 22, 2015, 02:34:06 pm »
I think the PSU is the same as in the 8720A/B/C VNAs. These are available. Download and check against the different versions.
If that turns out to be correct, keep us posted please about the version (not even sure there are much/any differences, its been a while since I repaired mine).

thank you ,I have checked HP8720 series from HP(keysight) website,there is service manual for 8720A/B/C,but this manual no refer to any component table or schematic for any section of machine.
Now when my 8751A turn on,it comes a error message "A and B channel overload".Before that it had burned something so not turn on,my friend replaced a "fuse resistor" in PSU,it turned on and worked OK,but when he used screw to "lock" PSU back to machine,it came out error,no idea to recover.I consider it should be PSU problem.
BH7JUO Mark
 

Offline mrf245Topic starter

  • Regular Contributor
  • *
  • Posts: 79
  • Country: cn
Re: HP8751A network analyzer schematic needed
« Reply #3 on: April 10, 2015, 08:32:14 am »
I just success repaired my 8751A and it worked fine now.I have checked main PSU,this model and schematic extremely similar to HP8753A/B module but 8751 with one more output line.It's no problem.Next I found post reg(08751-66540),most of output LED flashed once after power-on but no continuous output,I considered some protect signal cause it.I checked this PCB carefully and compare it with HP8753A/B schematic post reg,found they have some common design method,but some are really different.So I tried to find which signal cause protection.I finally found one of them come out from FAN behind mechine, yellow line,if this line rise up to 5V,it means FAN no working.This time FAN really no working.I checked along with FAN power line,and found a fuse resister(1A) on post reg board was burned.I used a fuse to replace it,repower-on,and it worked fine and made very sharp test.
I really appreciated keysight library Le,he helped me find 8751 service manual on library bookbox,even if no scanfiles.
I hope this repair can help people who need help like this.
BH7JUO Mark
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf